Greenhouse Gases Mapped from Space

Jet Propulsion Laboratory News Release

2008 October 9

PASADENA, Calif. - A NASA/university team has published the first global
satellite maps of the key greenhouse gas carbon dioxide in Earth's
mid-troposphere, an area about 8 kilometers, or 5 miles, above Earth. The team's
study reveals new information on how carbon dioxide, which directly contributes
to climate change, is distributed in Earth's atmosphere and moves around our
world.

A research team led by Moustafa Chahine of NASA's Jet Propulsion Laboratory,
Pasadena, Calif., found the distribution of carbon dioxide in the
mid-troposphere is strongly influenced by major surface sources of carbon
dioxide and by large-scale atmospheric circulation patterns, such as the jet
streams and weather systems in Earth's mid-latitudes. Patterns of carbon dioxide
distribution were also found to differ significantly between the northern
hemisphere, with its many land masses, and the southern hemisphere, which is
largely covered by ocean.

The findings are based on data collected from the Atmospheric Infrared Sounder
(AIRS) instrument on NASA's Aqua spacecraft between September 2002 and July
2008. Chahine, the instrument's science team leader, said the research products
will be used by scientists to refine models of the processes that transport
carbon dioxide within Earth's atmosphere.

"These data capture global variations in the distribution of carbon dioxide over
time," Chahine said. "These variations are not represented in the four
chemistry-transport models used to determine where carbon dioxide is created
and stored."

Chahine said the AIRS data will complement existing and planned ground and
aircraft measurements of carbon dioxide, as well as upcoming satellite missions
to study Earth's carbon cycle and climate. Included in the new satellite
missions is NASA's Orbiting Carbon Observatory, planned for launch in January
2009. The combination of carbon dioxide data from AIRS and the Orbiting Carbon
Observatory will allow scientists to determine the distribution of carbon
dioxide in the lower atmosphere, above Earth's surface.

"Carbon dioxide is difficult to measure and track," he said. "No place on Earth
is immune from its influence. It will take many independent measurements,
including AIRS, to coax this culprit out of hiding and track its progress from
creation to storage."

The new maps reveal enhanced concentrations of carbon dioxide south of the
northern hemisphere jet stream, in a band between 30 and 40 degrees north
latitude. These enhanced concentrations correspond to a well-documented belt of
pollution in the northern hemisphere mid-latitudes.

The team attributed the increased levels of carbon dioxide detected over the
western North Atlantic to emissions transported from the Southeast U.S. on warm
atmospheric "conveyor belts." These belts lift carbon dioxide from Earth's
surface into the middle and upper troposphere. The AIRS maps also showed
enhanced carbon dioxide over the Mediterranean, resulting from North American
and European sources. Carbon dioxide from South Asia ended up over the Middle
East, while carbon dioxide from East Asia flowed out over the Pacific Ocean.

In the southern hemisphere, a belt of mid-tropospheric air containing enhanced
concentrations of carbon dioxide emerged between 30 and 40 degrees south
latitude. This belt had not previously been seen in the four chemistry-transport
models used in this study. The researchers say the flow of air in this belt over
South America's high Andes Mountains lifts carbon dioxide from major sources on
Earth's surface, such as the respiration of plants, as well as forest fires and
facilities used for synthetic fuel production and power generation. A portion of
this lifted carbon dioxide is then carried into the mid-troposphere, where it
becomes trapped in the mid-latitude jet stream and transported rapidly around
the world. "The troposphere is like international waters," Chahine said. "What's
produced in one place will travel elsewhere."

Study results were published recently in Geophysical Research Letters. Other
participants included the California Institute of Technology, Pasadena, Calif.;
and the University of California, Irvine.